1. Field of the Invention
Some embodiments of this invention relate to the field of autonomous navigation and load parameter estimation by Unmanned Aerial Vehicles (UAVs) by passively emitted Electro Magnetic Fields (EMFs) from power lines.
2. Discussion of Related Art
Current methods of UAV navigation can be characterized as active, in that the flight path is commanded by radio, or follows a planned route defined by waypoints and guided by an absolute position reference system like GPS. There have been attempts to navigate by power lines, with varied success. A recent paper [Moore, J. and Tedrake, R., “Powerline Perching with a Fixed-Wing UAV”, Proceedings of the AIAA Infotech@Aerospace Conference, Seattle, Wash., April 2009] used a particle filter in conjunction with simulated magnetic fields to guide a UAV to a power line perch. Although based on magnetic field models, the method reduces a 3-phase circuit to a single magnetic dipole model, which discards much of the detail necessary to fly at close range to the lines. Locally generated underwater electromagnetic signals have been used for navigation of Autonomous Underwater Vehicles (AUVs) [Sanford, T., and Tyler, R., “Nearshore Navigation and Communication Based on Deliberate EM Signals”, Applied Physics Laboratory, University of Washington, 2005], although the sensors used for this purpose are quite large and not appropriate for a UAV.
Therefore, there is a need for refinement of autonomous UAV navigation systems to support following the power lines to a predetermined destination with little or no a priori information about location of the lines within a power grid.